$γγ\to πππ$ to One Loop in Chiral Perturbation Theory

Abstract

The $γγ\to π^0 π^0 π^0$ and $γγ\to π^+ π^- π^0$ amplitudes are discussed in the general context of Chiral Perturbation Theory (ChPT) to $O(p^6)$. Chiral loops are found to play a major role. This makes these processes a good test of ChPT, mainly in its anomalous sector. We correct earlier numerical results at tree level and determine the one-loop results as well.